The objectives of this numerical model study were to: (a) identify the major sources of sediment causing shoaling in the South Fork, St. Lucie Estuary, (b) determine the water discharge threshold at which substantial quantities of sand begin to move in the canal, (c) forecast the expected value of future shoaling rates in the South Fork, St. Lucie Estuary, (d) determine if an overgate release of water would produce less turbidity than the present undergate release, and (e) assess the adequacy of existing field data and recommend modifications to the data collection program as necessary. To meet these objectives, numerical models of the systems were developed. The computer code 'HEC-6, Scour and Deposition in Rivers and Reservoirs,' was used for the canal study area and four numerical models fo the estuary were developed. Two of the estuary models analyzed shoaling and scour using field survey data. A two-dimensional hydrodynamic model was developed to investigate water current patterns. The fourth model, an HEC-6 model, of the area downstream of the St. Lucie lock, was used to forecast future quantities of sand discharge into the estuary and enable a prediction of future shoaling conditions. The laterally averaged, two-dimensional model, LARM, was used to study the relative effect of overgate versus undergate release on the vertical distribution of velocity in addressing the turbidity question.